Power combiners are known from the following documents, for example: EP 0 210 606 A2, DE 27 33 888 A1, US 2014/0292441 A1, EP 1 347 532 A1.
The output power of high-frequency (HF) signal sources, in particular of HF transistor amplifiers, is limited to from several 100 W to a few kW. In order to achieve a higher output power, a plurality of high-frequency signal sources therefore have to be interconnected by a power combiner. The power combiners are intended to have losses that are as small as possible for a large bandwidth.
At the same time, however, the inputs of the power combiner, to which inputs the high-frequency signal sources can be connected, are intended to be insulated from one another as well as possible, in order to prevent transverse supply of the high-frequency signal sources and an uneven distribution of reflected output power. Unequal amplitudes, phases or internal impedances of the high-frequency signal sources connected to the power combiners result in particular in a push-pull signal that is detrimental to the high-frequency signal sources. Additionally or alternatively thereto, when the distribution of the reflected power is unequal, the phases and/or amplitudes and the load impedance of the individual amplifiers can vary. This can lead to excessive stress on the amplifier that is the most heavily loaded.
The high-frequency signal sources connected to the inputs of a power combiner can be protected when the frequencies of the high-frequency signal sources are constant. However, for matching to a load that can be connected to an output of the power combiner, the high-frequency signal sources connected to the inputs of the power combiner are operated at a variable frequency (known as a frequency tuning operation). It is therefore desirable to provide a power combiner of which the inputs are significantly better matched and insulated in the event of unequal amplitudes, phases or internal impedances of high-frequency signal sources connected to the inputs, even in the event of frequency changes.